FAME (v1.0): a simple module to simulate the effect of planktonic foraminifer species-specific habitat on their oxygen isotopic content

Didier M Roche,Brett Metcalfe,Claire Waelbroeck,Thibaut Caley

doi:10.5194/gmd-11-3587-2018

Abstract

Abstract. The oxygen-18 to oxygen-16 ratio recorded in fossil planktonic foraminifer shells has been used for over 50 years in many geoscience applications. However, different planktonic foraminifer species generally yield distinct signals, as a consequence of their specific living habitats in the water column and along the year. This complexity is usually not taken into account in model–data integration studies. To overcome this shortcoming, we developed the Foraminifers As Modeled Entities (FAME) module. The module predicts the presence or absence of commonly used planktonic foraminifers and their oxygen-18 values. It is only forced by hydrographic data and uses a very limited number of parameters, almost all derived from culture experiments. FAME performance is evaluated using the Multiproxy Approach for the Reconstruction of the Glacial Ocean surface (MARGO) Late Holocene planktonic foraminifer calcite oxygen-18 and abundance datasets. The application of FAME to a simple cooling scenario demonstrates its utility to predict changes in planktonic foraminifer oxygen-18 to oxygen-16 ratio in response to changing climatic conditions.

Highlights

Since the early work of Emiliani (1955), oxygen-18 isotopic abundance in calcite fossil foraminifer tests recovered from oceanic sediments has been widely used to reconstruct the past variations in oxygen-18 content of seawater as well as its temperature, the two main variables that affect the ratios of oxygen-18 to oxygen-16 in calcite
Foraminifers As Modeled Entities (FAME) is only forced by hydrographic data and only uses six parameters per planktonic foraminifer species that are all derived from culture experiments, plus one parameter accounting for the effect of the accretion of a calcite crust by N. pachyderma
Since the depth parameter was constrained using the MARGO Late Holocene dataset by error minimization, it is not surprising that the errors obtained with FAME are very small on average for each species considered (Fig. 2)

Summary

Introduction

Since the early work of Emiliani (1955), oxygen-18 isotopic abundance in calcite fossil foraminifer tests recovered from oceanic sediments has been widely used to reconstruct the past variations in oxygen-18 content of seawater as well as its temperature, the two main variables that affect the ratios of oxygen-18 to oxygen-16 in calcite (hereafter R18Oc). Increased plankton sampling (Bé and Tolderlund, 1971) and the advent of the sediment trap have shown that different species have different living habitats in the water column and throughout the year and that in some cases the foraminiferal R18Oc presents an offset with respect to the equilibrium calcite oxygen-18 to oxygen ratio (Mix, 1987; Bijma and Hemleben, 1994; Ortiz et al, 1995; Kohfeld et al, 1996; Bauch et al, 1997; Schiebel et al, 2002; Simstich et al, 2003; Mortyn and Charles, 2003; Rebotim et al, 2017; Jonkers and Kucera, 2015). To correctly interpret the wealth of information coming from the calcite oxygen-18 to oxygen-

Methods

Results

Conclusion